/Engine/Source/Runtime/GeometryCore/Public/DynamicMeshEditor.h
Project triangles onto a plane defined by the ProjectionFrame and use that to create/set new shared per-triangle UVs.
void SetTriangleUVsFromProjection ( const [TArray](API\Runtime\Core\Containers\TArray)< int > & Triangles, const [FFrame3d](API\Runtime\GeometryCore\FFrame3d_1) & ProjectionFrame, const FVector2f & UVScale, const FVector2f & UVTranslation, int UVLayerIndex, bool bShiftToOrigin, bool bNormalizeBeforeScaling )